Designers and manufacturers of high speed vehicles seek to increase performance and improve the quality of the ride experienced by passengers. For this reason, passenger seats on high-performance watercraft may be provided with padding and shock absorbers to attenuate mechanical shocks.
U.S. Pat. No. 5,810,125 to Gezari refers to an active shock-absorbing seat system for high-speed, high-performance watercraft. In the Gezari system, accelerometers coupled to the seat and deck and sensors within the shock-absorbing system sense the watercraft motion, and actively-controlled shock absorbers connected to the passenger seats use the sensor information to reduce the accelerative forces experienced by passengers.
U.S. Pat. No. 4,363,377 to Van Gerpen refers to an active suspension system for controlling a tractor seat during low frequency jolts and bumps. The Van Gerpen system aims to maintain the seat within a substantially horizontal plane as the tractor moves up and down. In the Van Gerpen system, the control is based on a mass vibrometer located within a tractor.
U.S. Pat. No. 6,059,253 to Koutsky discloses a suspension system for controlling a vehicle seat for up to six different types of motions (six degrees of freedom). The suspension system is also intended to act as a structural support for the seat. Koutsky relies on movement and position sensors located within the vehicle. As the vehicle encounters a bump, the sensors provide feedback to a control unit, which controls the seat suspension system. The entire disclosure of the Koutsky patent is incorporated herein by reference.
Known shock absorbers and seat control systems are not able to effectively attenuate the effects of shocks, such as mechanical shocks caused by a watercraft striking waves at high speed. For example, during high speed maneuvering in high performance watercraft, successive collisions with waves may cause a passenger to repeatedly experience shock events including brief accelerations as high as nine Gs (i.e., nine times the normal force of gravity) or more. The shock events may recur periodically, for example once every one and one-half seconds. Currently available systems are unable to adequately attenuate such disturbances, due in part to the short duration and large amplitude of the disturbances, and also because the event timing may be irregular.